Graphene foam as current collector in a Li-S type battery*

Sulfur has shown great potential as an active material for use in lithium-ion batteries. In the past decade, much research has been devoted to overcoming the problems of electrode expansion during cycling and the shuttle effect whereby sulfur deposits form on the lithium anode leading to cell failure, in addition to the dendrite growth. Electrodes are typically made by casting a slurry composed of the active material plus binding agents onto aluminum or copper foils, yielding an electrode layer with a thickness in the range of 50 μm. Cell performance can be limited by the electrode thickness due to the need for ions to diffuse through the active layer. With this in mind, we have incorporated graphene foam as a current collector which allows for high mass loading of active material while maintaining performance. Here, we compare the performance of graphene foam electrodes to a typical electrode made by the doctor blade method. The graphene foam allows for superior mass loading while also mitigating the loss of cell performance typical at high discharge rates. We also use Raman spectroscopy to observe changes in the electrode during the first discharge as the solid-electrolyte interphase is formed.